The present invention is based on a fuel injector according to the preamble of Claim 1 and a method of operating a fuel injector according to the preamble of Claim 10.
The closing times of fuel injectors are lengthened by adhesion forces between armature and core, as well as by eddy currents. It is known that delays can be reduced by making a current flow through the solenoid in the reverse direction at the end of the current pulse which excites the fuel injector in order to accelerate the decay of the residual field. The design of the corresponding control element is, however, complex and also only results in a slight shortening of the closing time.
Another option is to build up one magnetic field to open the fuel injector and a second magnetic field to hold the fuel injector in its open position. The intensity of the holding field can then be selected to be sufficiently low for the eddy currents to be small after the holding field is shut off, and thus the closing time can be shortened.
German Patent 23 06 007 C3 describes an electromagnetically actuated fuel injector for injecting fuel into an internal combustion engine in which the solenoid has three windings, which are supplied by three separate circuits. The first circuit is used for rapidly opening the fuel injector, the second circuit is used for holding the fuel injector open, and the third circuit is used for generating a counterfield extinguishing the residual magnetic field in order to rapidly close the fuel injector.
The disadvantage of the fuel injector known from German Patent 23 06 007 C3 is in particular the complex manufacturing process of an arrangement having three circuits, which supply three windings of the solenoid. The increased space required by the circuits is another disadvantage. No active resetting through a magnetic force component acting in the closing direction takes place.